Commodore 1571 firmware
Get Active Buffer Numbe
.page
.subttl 'getact.src'
;*********************************
;* getact: get active buffer # *
;* vars: buf0,buf1,lindx *
;* regs: out: .a= act buffer # *
;* .x= lindx *
;* flags: .n=1: no act-buf *
;*********************************
getact
ldx lindx
lda buf0,x
bpl ga1
lda buf1,x
ga1
and #$bf ; strip dirty bit
rts
;*********************************
;* gaflg: get active buffer #; *
;* set lbused & flags. *
;* regs: out: .a= act buffer # *
;* .x= lindx *
;* flags: .n=1: no act-buf *
;* .v=1: dirty buf *
;*********************************
gaflgs
ldx lindx
ga2 stx lbused ; save buf #
lda buf0,x
bpl ga3
txa
clc
adc #mxchns+1
sta lbused
lda buf1,x
ga3
sta t1
and #$1f
bit t1
rts
;******************************
; get channels inactive
; buffer number.
; input parameters:
; lindx - channel #
; output parameters:
; a <== inactive buffer #
; or
; a <== $ff if no
; inactive buffer.
;******************************
getina ldx lindx
lda buf0,x
bmi gi10
lda buf1,x
gi10 cmp #$ff
rts
;*****************************
;********** p u t i n a ****
;*****************************
; put inactive buffer
; input paramters:
; a = buffer #
; output paramters:
; none
;*****************************
putina ldx lindx
ora #$80
ldy buf0,x
bpl pi1
sta buf0,x
rts
pi1 sta buf1,x
rts